The neurite-stimulating activity of components of the salivary gland secretion of the medicinal leech in cultures of sensory neurons

Morphological and functional characterization of leech circulating blood cells: role in immunity and neural repair

Unlike most invertebrates, annelids possess a closed vascular system distinct from the coelomic liquid. The morphology and the function of leech blood cells are reported here. We have demonstrated the presence of a unique cell type which participates in various immune processes. In contrast to the mammalian spinal cord, the leech CNS is able to regenerate and restore function after injury. The close contact of the blood with the nerve cord also led us to explore the participation of blood in neural repair. Our data evidenced that, in addition to exerting peripheral immune functions, leech blood optimizes CNS neural repair through the release of neurotrophic substances. Circulating blood cells also appeared able to infiltrate the injured CNS where, in conjunction with microglia, they limit the formation of a scar. In mammals, CNS injury leads to the generation of a glial scar that blocks the mechanism of regeneration by preventing axonal regrowth. The results presented here constitute the first description of neuroimmune functions of invertebrate blood cells. Understanding the basic function of the peripheral circulating cells and their interactions with lesioned CNS in the leech would allow us to acquire insights into the complexity of the neuroimmune response of the injured mammalian brain.

Silencing of Rho-GDIgamma by RNAi promotes the differentiation of neural stem cells

RNA interference (RNAi) technology is one of the main means in the study of stem cell differentiation. This study describes Rho-GDIgamma function during the differentiation of neural stem cells by using RNAi. Rho-GDIgamma belongs to the Rho-GDI protein family, which is expressed at high level throughout the brain. Although it exists in neuronal population, its physiological function is poorly understood. By using RNAi technology to downregulate expression of Rho-GDIgamma, we found distinct morphological changes in neural stem cell line C17.2. More important, RT-PCR confirmed that RNAi-mediated downregulation of Rho-GDIgamma decreased expression of Rho-GDIgamma-regulated genes RhoA and slightly increased expression of Rac1. Further, immunochemical staining indicated that downregulation of Rho-GDIgamma increased the tendency of C17.2 cells to differentiate. These data strongly suggest that Rho-GDIgamma plays a key role in the differentiation of neural stem cells.